Transfer RNA and the formation of the heme and chlorophyll precursor, 5-aminolevulinic acid.
5-Aminolevulinic acid is the first committed precursor for the synthesis of porphyrins such as hemes and chlorophylls. In many organisms aminolevulinate is synthesized from glutamate in a three-step pathway (C5 pathway). The key step in this conversion is a tRNA-mediated reduction of glutamate to glutamate-1-semialdehyde. tRNA is a specific cofactor for an NADPH-dependent enzyme, Glu-tRNA reductase, which is capable of sequence-specific recognition of Glu-tRNA(Glu). tRNA(Glu) is a dual-function molecule; it participates both in protein and in aminolevulinate biosynthesis. This reduction reaction represents a novel role for tRNA where it participates in a metabolic conversion of its amino acid into a low molecular weight metabolite which is subsequently not used in peptide bond synthesis.
O'Neill
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Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
Söll
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D000445:Aldehyde Oxidoreductases / Q000378:metabolism; D000622:Aminolevulinic Acid / Q000378:metabolism*; D001483:Base Sequence; D002734:Chlorophyll / Q000096:biosynthesis*; D005975:Glutamate-tRNA Ligase / Q000378:metabolism; D006418:Heme / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012352:RNA, Transfer, Glu / Q000235:genetics* / Q000378:metabolism
D012352:RNA, Transfer, Glu; D002734:Chlorophyll; D006418:Heme; D000622:Aminolevulinic Acid; D000445:Aldehyde Oxidoreductases; C067282:glutamyl tRNA reductase; D005975:Glutamate-tRNA Ligase